A variety of modern electronic devices include a battery to supply power to the electronic device. Often, these batteries are rechargeable. For example, laptops, tablet computers, smart phones, and other such devices include a rechargeable battery. As such, a user may charge the device, or rather; charge the battery, and the battery can be used to supply power to the device during periods where other sources of power might not be readily available or convenient to use.
Rechargeable batteries used in such electronic devices include those having a number of secondary cells. For example, lithium-ion and lithium-ion polymer batteries include a number of secondary cells. Each of the secondary cells includes a positive and negative electrode, separated by an ion permeable material. The secondary cells may be electrically connected (e.g., in parallel) and enclosed in a metal case or disposed in a pouch to form a “battery pack.” A benefit of lithium based secondary cells is their ability to be repeatedly charged and discharged as well as their high volumetric energy densities.
As will be appreciated, however, lithium based rechargeable batteries have narrow tolerance values for charging, discharging, and operating temperature. Said differently, lithium based battery packs should not be overheated, overcharged, or discharged past a specific limit. In extreme cases of overheating or overcharge, the battery pack can rupture and/or combust. Furthermore, when the battery pack is discharged past a specific limit, it may be unusable and/or unsafe to recharge. As such, these battery packs demand a number of safety measures to prevent failures and ensure safety during operation. Accordingly, such battery packs are usually provided with a battery protection circuit for reducing and/or preventing over-charging, over-discharging, and out of temperature operation of the secondary cells.